1. Field of The Invention
The present invention relates to a process for the alkylation of organic aromatic compounds. In particular the invention relates to the alkylation of benzene with propylene to produce cumene. More particularly the invention relates to a process for the concurrent alkylation and distillation of reaction components (reactants and products) in a catalyst bed wherein the catalyst also serves as the distillation structure. Most particularly, the catalyst utilized is a dual bed of Omega and Y type molecular sieves.
2. Related Art
Recently a new method of carrying out catalytic reactions has been developed, wherein the components of the reaction system are concurrently separable by distillation, using the catalyst structures as the distillation structures. Such systems are described variously in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,302,356; 4,307,254; 4,336,407; 4,439,350; 4,443,559; and 4,482,775 commonly assigned herewith.
Briefly, a structure described there is a cloth belt with a plurality of pockets spaced along the belt, which is then wound in a helix about a spacing material such as stainless steel knitted mesh. These units are then disposed in the distillation column reactor. In addition, commonly assigned U.S. Pat. Nos. 4,443,559 and 4,250,052 disclose a variety of catalyst structures for this use and are incorporated herein.
Ethylbenzene and cumene are currently produced by the reaction of benzene and the respective olefin, i.e., ethylene and propylene by acid catalysis. In some known processes the catalyst is highly corrosive and has a relatively short life, e.g., AlCl.sub.3, H.sub.3 PO.sub.4 on clay, BF.sub.3 on alumina, and others require periodic regeneration, e.g., molecular sieves. The exothermicity of the reaction and the tendency to produce polysubstituted benzene require low benzene conversions per pass with large volume recycle in conventional processes. Advantages of the present invention are that the catalysts are not highly corrosive and may not require periodic regeneration, the heat of reaction is used efficiently, only low volume is required and the feed ratios can approach unity.
A catalytic distillation process for the production of cumene is disclosed in co-pending U.S. patent application Ser. No. 07/122,485, where a single bed of either acid cation exchange resin or a type Y molecular sieve catalyst was used.
The inventors herein have discovered a process for the alkylation of benzene with propylene that takes advantage of the higher selectivity of the Omega type sieves while reducing the amount of undesirable olefins in the cumene product.